Potassium channels are a diverse group of ion channels which are involved in virtually all aspects of membrane electrical behavior. Potassium channels are virtually ubiquitous among the cells of eukaryotes and the most heterogeneous of the voltage-gated cation channels. Because K+ channels are universally involved in membrane excitability, it is likely that most aspects of behavior and higher brain function in animals involves potassium channels in some way. In order to understand the significance of the great molecular diversity of K+ channels to behavior and many aspects of cell biology, we need to know the full extent of this diversity. The first aim of this proposal is to identify the full "set" of genes encoding voltage-dependent potassium channels in Drosophila. The relatively tiny Drosophila genome presents an opportunity to define the complete set of potassium channels in a single animal. It is our hypothesis that voltage- gated ion channels evolved nearly optimal structures prior to the separation of vertebrate and invertebrate species. Thus, all higher forms of life may share the same essential "set" of excitable channels. To verify this we propose to clone and express from mouse, any new K+ channel genes first isolated in Drosophila. Additional aims are: 1. to reveal the biophysical properties of each type of cloned channel by using the Xenopus oocyte expression system; 2. to determine whether cloned K+ channel subunits define separate K+ channel subfamilies or whether they mix to form heteromultimeric channels with subunits from other genes; 3. to determine the in vivo properties of cloned K+ channels, and their cellular and subcellular distributions. Underlying the multiplicity of potassium channel genes is their heterogeneity of function; determining both the functional properties and cellular distribution of the different potassium channels may reveal insights into their function. The techniques to investigate these questions will involve genetics, Northern analysis, PCR and immunocytochemistry.